An image forming apparatus performs an image adjustment so that a position or density of an image is not deviated. A sequence of such image adjustment includes, for example, forming a registration pattern, which is a mark for adjusting positional deviation, on a belt member for sheet conveyance for each of colors, acquiring a degree of deviation between the registration pattern of a basic color and the registration pattern of a detection target color and correcting positional deviation of an image of the detection target color based on a correction value specified based on the degree of deviation.
A correction value may be input by a user. For example, JP-A-2002-244393 describes a method of using both a correction value input by a user (manual correction value) and a correction value obtained by detection of a registration pattern (automatic correction value) to correct positional deviation of each color image in a color image.